05 October 2013

As a senior at MIT in 2011,
John Romanishin proposed a new approach to modular robotics that relied
on magnets, flywheels, and the laws of physics. While his mentors and
colleagues were skeptical his designs could work, Romanishin persevered
and continued developing the design. Now as a researcher at MIT’s
Computer Science and Artificial Intelligence Laboratory (CSAIL),
Romanishin has partnered with professor Daniela Rus and postdoc Kyle
Gilpin to make the M-Block robots a reality. Each one is a tiny
self-contained cube that can leap through the air and connect to other
M-Blocks to form larger modular robots — it’s a little like Voltron, but
with cube-shape robots instead of lions.

When studying modular
robots, researchers often use the sliding-cube model. This is a
simplified design concept where two cubes are connected face-to-face,
but can also slide up and over each other without changing orientation.
This model is useful for developing the algorithms that govern self-assembly,
but building a working version of the model is surprisingly difficult.
Most existing modular robots utilize various motors for movement and are
“statically stable,” meaning the motion can be paused at any point.

The M-Block simplifies
everything by doing away with complicated motors and actuators. They can
roll across the ground, leap on top of each other, and even climb
metallic surfaces alone or as part of a group. There are no external
arms or wheels on the M-Block robots — all the momentum for these feats
comes from a high-speed flywheel inside the cube. It can reach speeds as
high as 20,000rpm, and when the wheel is stopped, all that angular
momentum can toss the small cube a fair distance.

The flywheel is good at
getting the M-Blocks moving, but stopping them is a different matter
entirely. Romanishin’s design includes a pair of small cylindrical
magnets on each edges of the cube. The magnets are mounted on a tiny
spinning axle so that as one cube approaches the other, the magnets can
rotate so the opposite poles connect. Thus, any face of any two M-Block
robots can link to each other. All the robot needs to do is use the
flywheel to send itself tumbling or jumping in the general vicinity of a
second M-Block, and they’ll connect. That’s really the strength of this
system — a single component can move just fine on its own. If something
falls off or is damaged while completing a task, that’s not an
insurmountable problem.

A prototype of a new modular robot, with its innards exposed and its flywheel — which gives it the ability to move independently — pulled out. Credit: M. SCOTT BRAUER

The team believes the M-Block concept can
be expanded to include specialized sub-types of cubes that carry useful
hardware components. For example, one may have a camera, and another
could haul around a GPS chip. Even the exterior could be altered for
different purposes, like cubes with textured surfaces for moving more
effectively across rough terrain. The MIT
researchers are in the process of building a small army of 100 cubes to
see if they can be used to efficiently construct larger robots that can
stand in for chairs, tables, and even building scaffolding in an
emergency.